These studies are directed toward identification of the subset of nonhistone chromatin proteins which control the expression of specific genes during differentiation of teratocarcinoma cells. A DNA probe complementary to the most abundant class of poly(A)-containing RNA's from embryoid bodies and teratoma tumors will be used to determine the specificity of in vitro RNA transcription templated by either embryoid body chromatin or teratoma chromatin. It has been shown that the 5M urea soluble proteins from chick oviduct chromatin contains putative tissue-specific molecules which control transcription of ovalbumin messenger RNA. The 5M urea soluble proteins of embryoid body and teratoma chromatin will be similarly tested by reconstitution of teratoma chromatin urea soluble proteins to the embryoid body DNA-tightly binding protein complex (the reciprocol experiment will also be done) in order to establish that the analogous activity exists in the 5M urea soluble chromosomal proteins from teratoma or embryoid body chromatin. A 2-dimensional gel electrophoresis of the subset of non histone proteins, conferring transcriptive specificity to chromatin, will be used to analyze radiolabeled nonhistone proteins in order to identify that subset of nonhistones involved in gene regulation.